The long-term objective of this research project is to delineate the mechanisms by which glucose transport activity is regulated in rat thymocytes. The Km and Vmax values for the two phases of 3-O-methylglucose uptake for unstimulated cells and for cells in which transport activity has been stimulated by anoxia, uncouplers, sulfhydryl reagents, Concanavalin A, and heat treatment. An autoradiographic technique will be developed for visualizing the relative rates of glucose transport among different subpopulations of thymocytes. Plasma membranes will be prepared from rat thymocytes and characterized with regard to protein composition using SDS-polyacrylamide gel electrophoresis. Using a double labeling procedure combined with SDS-gel electrophoresis, an attempt will be made to identify a cortisol-induced protein that inhibits glucose transport in these cells. The relative effects of plant lectins in inducing blast transformation and transport stimulation will be studied to see if the two phenomena are related. stimulation of transport activity will be investigated in Ca 2 ion-depleted cells in an attempt to discern the role of Ca 2 ion in transport stimulation. Finally, attempts will be made to prepare membrane vesicles that retain regulatory control of glucose transport activity.